I've always had a hard time immediately understanding the differences between passive, causative, and causative-passive. If I really sit down and try to work out the meaning I can generally get it, but I have a bad habit of just skimming over it.

One verb that is giving me trouble is 笑う:

The passive is 笑われる, or "to be laughed at". This seems pretty straight-forward.

たけしさんはメアリーさんによく笑われます。 Takeshi is often laughed at by Mary.

The causative is 笑わせる, or "to make laugh, to let laugh". Again, this makes sense to me.

彼は子供達を笑わせた。 He made the children laugh.

What I don't understand is the the causative-passive, 笑わせられる. My understanding of it is that it follows the pattern of "is made to do", that someone is made to do something that they don't want to do. But how does this work with laughter? It seems to me that this is the same meaning as "being made to laugh". The only other thing I can think of is "was made to laugh at someone", like in a peer-pressure sort of situation.

Take this JLPT practice question:

△△さんの冗談には、いつも思わず 笑わせられた 。

The wrong answers include 笑われた, and 笑わせた.

Why is the answer the causative-passive (せられた), and not the causative (せた)? What is the difference in meaning? Is the causative out-right wrong here, or is it just less-right or natural then the causative-passive? Is there a clue in the sentence structure that I'm missing?

In your last sentence, 私が must be 私は. In addition, although this sentence can indeed be called “more complete,” stating an obvious subject makes it less natural.
– Tsuyoshi ItoSep 21 '12 at 0:33

@TsuyoshiIto Thanks, I thought は sounded more natural, too, but thought I could get away with が... Anyway, corrected.
– Earthliŋ♦Sep 21 '12 at 3:18

"You can't say 冗談が私を笑わせた。" I disagree. 彼の冗談は私を笑わせた sounds completely natural to me. The point of the passive is not to avoid 冗談 being the subject, but to add the nuance of involuntariness, as Teno's answer suggests.
– dainichiSep 21 '12 at 7:55

I agree with your example. I, too, believe 彼の冗談は私を笑わせた is natural and correct. But in this example 彼の冗談 is the topic of the sentence; the sentence 彼の冗談が私を笑わせた sounds unnatural, because が indicates 冗談 as subject, and this is what mustn't happen. In Japanese, a joke can't make someone laugh directly, but can, of course, be the reason (indicated by は) for someone to be made to laugh...
– Earthliŋ♦Sep 21 '12 at 14:58

1

@silvermaple に(は) indicates 冗談 as indirect object (and the topic of the sentence). 冗談には makes only sense as indirect object for 笑わせられた. 笑わせた doesn't take an indirect object and 笑われた would mean the joke laughed at you...
– Earthliŋ♦Sep 22 '12 at 1:27